1. Field of the Invention
The present invention relates to a deflection yoke that is used for a color cathode ray tube of a television receiver, a computer display, or the like and a color cathode ray tube device using the deflection yoke.
2. Related Background Art
Generally, in a deflection yoke, magnetic intensity is highest in a minor diameter portion, and thus a positional shift of the minor diameter portion in a ferrite core of the deflection yoke has a great influence on convergence properties. As a solution to this, the following technique has been disclosed in JP 5 (1993)-11292 U.
As shown in FIGS. 5 and 7, a deflection yoke includes a horizontal deflection coil 1, an insulation frame 2, a vertical deflection coil 3, and a ferrite core 4 having the general shape of a surface of a conical frustum, respectively that are arranged in this order outwardly. In the insulation frame 2, a plurality of elastic projections 5 are formed on an outer wall 2a of a minor diameter portion that are arranged in a standing condition symmetrically with respect to each other. The plurality of elastic projections 5 are in contact with an inner wall 4b of a minor diameter portion of the ferrite core 4 to control a positional shift of the ferrite core 4 in a horizontal direction. For fixing of the ferrite core 4 to the insulation frame 2, a major diameter portion 2b of the insulation frame 2 and a major diameter portion 4d of the ferrite core 4 are fixed to each other by a hot-melt adhesive 6.
FIG. 6 shows a cross section of the deflection yoke perpendicular to a tube axis Z. As shown in FIG. 6, generally, the vertical deflection coil 3 is substantially circular at an inner face but is substantially elliptical at an outer face, having a major axis in a direction of a horizontal axis X. That is, the vertical deflection coil 3 has a thickness that is smaller on a vertical axis Y than on the horizontal axis X. This has been a cause of the formation of a gap xcex42 in a direction of the vertical axis Y between an outer wall face of the vertical deflection coil 3 and the inner wall 4b of the minor diameter portion of the ferrite core 4.
In addition, when the ferrite core 4 is fitted to the insulation frame 2 in a process of assembling a deflection yoke, the following is observed. In the case where the inner wall 4b of the minor diameter portion of the ferrite core 4 has a tapered portion having a diameter decreasing in a direction towards an end side of the minor diameter portion as shown in FIG. 5, an elastic force exerted by the elastic projections 5 acts with respect to the tapered portion of the inner wall 4b of the minor diameter portion in a direction indicated by an arrow C that is oblique with respect to the tube axis Z. Similarly, in the case where end portions 5a of the elastic projections 5 are bent downward with respect to the inner wall 4b of the minor diameter portion of the ferrite core 4 as shown in FIG. 7, an elastic force exerted by the elastic projections 5 acts with respect to the inner wall 4b of the minor diameter portion in a direction indicated by an arrow C that is oblique with respect to a tube axis Z. Consequently, in both configurations described above, the elastic force exerted by the elastic projections 5 acts with respect to the ferrite core 4 in such a manner that the major diameter portion 4d of the ferrite core 4 is parted from the major diameter portion 2b of the insulation frame 2 in a direction of the tube axis Z. This has been a cause of the formation of a gap xcex41 in the tube axis direction between the vertical deflection coil 3 and the ferrite core 4.
As a result, when the deflection yoke as described above is fitted to a color cathode ray tube, the ferrite core 4 is shifted in directions of a vertical axis Y and a tube axis Z of the color cathode ray tube and thus cannot be held in an optimum position, which has been disadvantageous. This has been a cause of the generation of YH crossed misconvergence as shown in FIG. 8, which adversely affects image quality.
This invention is intended to solve the problems as mentioned above. It is a first object of the present invention to provide a deflection yoke in which a ferrite core can be held in an optimum position in a vertical axis direction. Further, it is a second object of the present invention to provide a deflection yoke in which a ferrite core can be held in an optimum position in a tube axis direction as well as in a vertical axis direction. Still further, it is a third object of the present invention to provide a color cathode ray tube device that can inhibit the generation of YH crossed misconvergence by holding a ferrite core in a desired position.
A deflection yoke of the present invention includes a horizontal deflection coil, an insulation frame, a vertical deflection coil, and a ferrite core that are arranged in this order outwardly. On an outer wall of a minor diameter portion of the insulation frame, a plurality of elastic projections are provided that are arranged in a standing condition to hold an outer wall of a minor diameter portion of the ferrite core.
According to this configuration, a center of the ferrite core is controlled so as to be positioned on a tube axis by the plurality of elastic projections.
Preferably, in the aforementioned configuration, on the outer wall of the minor diameter portion of the ferrite core, a tapered portion having a diameter decreasing in a direction towards an end side of the minor diameter portion is provided and held by the elastic projections.
According to this configuration, when the ferrite core is fitted to the insulation frame in an assembling process, the elastic projections apply an elastic pressing force in an oblique direction with respect to a tube axis direction to a surface of the tapered portion. Accordingly, a component of the elastic pressing force in the tube axis direction acts in such a manner that a major diameter portion of the ferrite core is pressed to a side of a major diameter portion of the insulation frame in the tube axis direction. This allows a position of the ferrite core in the tube axis direction to be controlled properly.
A color cathode ray tube device of the present invention includes the deflection yoke of the present invention as described above, thereby allowing the minor diameter portion of the ferrite core to be held in a desired position. Thus, an excellent image display in which the generation of YH crossed misconvergence is inhibited can be obtained.